Non VT-x or AMD-v CPUs vs enabled CPUs

[rightfoot]

I've been using ESX for a while, mostly with linux desktops. I haven't been doing much in terms of multimedia and now need to have more media enabled desktops of both windows and linux.

Currently, I'm using multi-cpu, multi-core blades for the hosting which don't have VT-x or AMD-v enabled on them. I was told that I absolutely must use enabled CPUs in order to gain media benefits but it's been difficult to really understand what those benefits might be.

For example, I installed a linux desktop server as a VM on ESX as a test and was able to receive audio from remote connections and did see video so what am I missing?

Could someone enlighten me, and perhaps others interested in understanding these capabilities and differences. I have an IBM 3655 which does have multiple AMD-v enabled CPUs and thought I might fire that up for testing but am not really sure what it is I would be testing :).

Thanks.

[RParker · Accepted solution]

Currently, I'm using multi-cpu, multi-core blades for the hosting which don't have VT-x or AMD-v enabled on them. I was told that I absolutely must use enabled CPUs in order to gain media benefits but it's been difficult to really understand what those benefits might be.

Not true. Multimedia is built in to the capabilities of the processor. VT-x is for virtualizing 64-bit OS. That's all it's for.

[rightfoot]

Part of that confusion comes from documentation which says that one must use hardware with virt-aware CPUs. So, this has nothing to do with gaining benefits for windows guests or anything else, it is simply to virtualise 64bit OS's?

[admin]

On current hardware, VT-x or AMD-V (especially with EPT or RVI) generally does outperform binary translation for most workloads. See this discussion.

VT-x is required for 64-bit guests on Intel CPUs; AMD-V is not required for 64-bit guests on AMD CPUs.

[RParker]

which says that one must use hardware with virt-aware CPUs.

The confusion comes from what people DON'T say.. CPU, meaning the CPU must support the instructions and codes for multi media. As I said, its built into the CPU, but it's there and available whether you "enable" it or not. VT-x is just a trigger in the BIOS to allow Virtulization software to talk to the hardware, at a certain hardware level so that 64-bit CPU can run in a VM. That's all it does.

The fact that VT-x is on or off, has no bearing on the capabilities of the CPU, those functions will work regardless, so it's not something that's disabled or ignored, it depends on the software and capabilities of the underlying OS. If you run ESX you can do a hardware passthru. If you use VM Server for instance, that has no such passthru, so on the same machine the capabilities are different, it only matters if the OS or the Hyper Visor can take advantage of the hardware. That's the confusion. People think that the two are connected, but they are not.

ONLY certain features of a CPU or chipset are settable, otherwise ALL of them function.

[rightfoot]

For example, I went and tried installing XenServer onto a dual duo-core system which are 64bit CPUs but without the virtualization in them and the server didn't even want to try. On the other hand, I then tried on a dual single core 64bit CPU system and that worked with the warning that unless I installed linux pack, I would only have linux servers allowed.

I have ESX installed on those 64bit blades and can install 64bit OSs but it sounded like I was missing out on something I didn't understand. I wanted to have more media capabilities for the guest win machines installed on these blades.

[admin]

To the best of my knowledge, XenServer requires hardware-assisted virtualization. VMware products on AMD hardware do not. You are not missing out on anything without AMD-V.